QEMU memory problem:

simulate 32 bit in 64 bit environment, we can use MAP_32BIT to force mmap to allocate memory address within 4G.
However, according to http://lxr.free-electrons.com/source/arch/x86/kernel/sys_x86_64.c, we can only get memory between 0x40000000 and 0x80000000,

atomic region

This project aims to efficiently handle guest instruction exception through atomic region (software approach).

Atomic region: blocked execution mode?

what is blocked execution mode

Installing Debian ARM under QEMU

from http://richizo.wordpress.com/2010/11/15/installing-debian-arm-under-qemu/ 

November 15, 2010

In this post I will explain how to install Debian Armel under QEMU.
Well, there are various reasons to you have a ARM Linux distro inside a Virtual Machine. One of them would be to have a test environment to you validate your programs before to release to an embedded linux (ARM).
Debian was choosed because is the most supported ARM distro and you will have an compatible environment with your embedded system (eglibc).
Hey! Ho! Let’s go:

• Download a ARM kernel and a vmlinuz image under debian.org FTP site (I choosed squeeze/testing flavor):

wget http://ftp.debian.org/debian/dists/testing/main/installer-armel/current/images/versatile/netboot/vmlinuz-2.6.32-5-versatile

wget http://ftp.debian.org/debian/dists/testing/main/installer-armel/current/images/versatile/netboot/initrd.gz

• Create a disk image (please, create a raw disk! It will be useful future):

qemu-img create -f raw debian.img 10G

• Start Debian image using qemu:

qemu-system-arm -m 256 -M versatilepb -kernel vmlinuz-2.6.32-5-versatile -initrd initrd.gz -hda debian.img -append "root=/dev/ram"

• After install Debian in the disk image, we will mount the contents of disk image:

sudo kpartx -av debian.img

sudo mount /dev/mapper/loop1p1 ./mnt/ -o loop

PS: I installed Debian with one only partition (/dev/sda1 is my root filesystem). Kpartx is needed because my disk image has 2 partitions (root filesystem and swap)

• Copy the initrd image and the kernel to your system (outside of mountpoint). These two files will be used to start our Debian installation:

cp ./mnt/boot/initrd.img .

cp ./mnt/boot/vmlinuz-2.6.32-5-versatile .

• Now, we can start Debian image installed in the disk image:

qemu-system-arm -m 256 -M versatilepb -kernel vmlinuz-2.6.32-5-versatile -initrd initrd.img -hda debian.img -append "root=/dev/sda1"

In the next posts I will talk about ARM architecture, toolchains, cross compilers and embedded linux. ;)

http://zhiwei.li/text/2010/12/qemu-system-arm%E8%BF%90%E8%A1%8Cversatilepb%E6%9C%80%E5%A4%9A%E5%8F%AA%E8%83%BD%E6%94%AF%E6%8C%81256m%E5%86%85%E5%AD%98/

Peter Maydell 在2010年11月29日有一个解释

http://comments.gmane.org/gmane.comp.emulators.qemu/86388

‘versatilepb’ also supports only 256MB of RAM, for the
same reason (system registers starting at 0×10000000).
You might try one of the realview models, which have a
special case for putting more RAM at a high memory address.

versatilepb 开发版也只支持256M 内存， 因为同样的原因（系统寄存器开始于 0×10000000), 你可以试试 realview模型，它可以将 更多的内存放置于高端地址

PARSEC

NOT RUN Benchmark:
ferret: can build, can run
raytrace: cannot build, need 32bit  libXmu libX11 libGL libGLU
vips: cannot build, python2.6 cannot agree with LONG_BIT:

In file included from /usr/include/python2.6/Python.h:58,

                 from /local/tk/research/llvm-qemu/benchmarks/parsec-2.1/pkgs/libs/libxml2/src/python/libxml_wrap.h:2,

                 from /local/tk/research/llvm-qemu/benchmarks/parsec-2.1/pkgs/libs/libxml2/src/python/types.c:9:

/usr/include/python2.6/pyport.h:685:2: error: #error "LONG_BIT definition appears wrong for platform (bad gcc/glibc config?)."

========================================================

All 13 benchmarks except vips, all can build successfully 

we have run 8 benchmarks, still have 4 benchmarks to try

ferret, raytrace, x264, dedup,
raytrace, x264, OK
ferret and dedup cannot run

use a list to 

dedup: tb_invalidate_phys_page in page_set_flags in target_mmap:559

qemu cannot run dedup because it mmap over 2G memory.

helper functions

      8 $adc_cc
   1991 $add_cc
     71 $clz
    885 $cpsr_read
   1547 $cpsr_write
    773 $exception
     21 $get_cp15
      8 $get_user_reg
     36 $sar
     44 $sbc_cc
    122 $set_cp15
     29 $set_user_reg
    479 $shl
     62 $shl_cc
    191 $shr
      8 $shr_cc
  32183 $sub_cc
      1 $wfi